Obesity currently poses a threat to public health in the industrialized nations and therefore is directly relevant to the mission of the NIMH to reduce the burden of behavioral disorders through research on the brain and behavior. It is also relevant to the mission of the NIDDK to study metabolic and endocrine disorders affecting public health using basic science. Binge eating of palatable foods is a behavioral characteristic of obesity and other eating disorders, making it of great clinical relevance and utmost importance to understand neural mechanisms underlying its behavior. Bingeing on palatable foods can induce behaviors and alterations in the brain that are similar to the effects of drugs of abuse;however, little is known about the neurochemical or molecular mechanisms underlying this phenomenon. The primary goal of this proposal is for me to learn and apply the techniques of in situ hybridization, immunohistochemistry, radioimmuno-assay and capillary electrophoresis to identify and characterize some common neural mechanisms underlying binge eating of palatable foods and drug use. This proposal will measure opioid and non-opioid peptide expression as well as amino acid release in areas of the brain that regulate both feeding behavior and drug dependence, namely, the lateral hypothalamus (LH) and nucleus accumbens (NAc). These analyses will be performed as a function of binge eating of palatable foods (fat vs. sugar) compared with ad libitum access to the food. In addition, measures of circulating levels of steroid hormones and lipids will be collected and related to these neurochemical changes in the brain. I propose to test the novel hypotheses that: 1) opioids and amino acids in the LH function in relation to the macronutrient content of a palatable food independent of access schedule, whereas in the NAc they function in relation to the binge eating resulting from intermittent access to a palatable food;2) these brain regions and their respective functions are connected via a population of non-opioid, orexigenic peptide neurons in the LH that project to the NAc;3) the circulating steroids and lipids, which are elevated by consumption of a palatable, high-fat diet, modulate the neurochemicals of the LH and NAc that contribute to the process of binge eating of fat- rich foods. This research will identify some neural and molecular mechanisms underlying binge eating associated with obesity, which is an important public health issue. Information about the processes in the brain underlying binge eating of fat-rich foods will be useful for developing treatments to reduce this behavior and ultimately the incidence of obesity.